During the last three decades, bone marrow transplantation (BMT) has become the standard care for the treatment of many hematological malignancies. The idea donor, one who possesses the same HLA-A, B, DR phenotype as that of the patient, is found less than 35% of the time among family members and less than 50% of the time among unrelated donors. Furthermore, minority patients have even lower probability of finding an HLA matched donor. The overall goals of this project are to evaluate the feasibility of finding unrelated matched donors for bone marrow transplant (BMT) patients as a function of HLA-A, B, DR phenotype, race and geographical location of recipient and donor, to develop projections which will facilitate management strategies for recruiting marrow donors on the basis of race and geographical location, and to develop tools which will permit analysis of clinical outcomes on the basis of the probability of haplotype match rather than phenotype match among unrelated BMT patients. Specific aims of the project are to: (1) compare HLA polymorphism among various racial groups and in different geographical regions of the United States; (2) estimate the probability of finding a 6/6 HLA-A, B, DR match and 6/6 or 5/6 match various racial groups as well as for geographically defined groups; (3) estimate the number of donors required from each racial group and geographical region in order to achieve equal access among various racial groups: (4) assess the extent to which European and other foreign marrow donor registries can assist U.S. patients in finding a matched donor by contributing to the diversity of phenotypes represented in the registry: (5) evaluate HLA polymorphism using DNA typing data and to estimate the probability of finding an HLA match at the level of allele rather than antigen for each racial group; (6) evaluate the impact of changes in matching criteria based on molecular determinations of phenotype upon the probability of finding a matched donor for each racial group; (7) develop tools which permit evaluation of impact of genotype match on clinical outcomes among unrelated BMT patients.